Plant and Soil

, Volume 278, Issue 1–2, pp 55–74 | Cite as

Observation and Simulation of Root Reinforcement on Abandoned Mediterranean Slopes

  • L. P. H. van Beek
  • J. Wint
  • L. H. Cammeraat
  • J. P. Edwards


The mechanics of root reinforcement have been described satisfactorily for a single root or several roots passing a potential slip plane and verified by field experiments. Yet, precious little attempts have been made to apply these models to the hillslope scale pertinent to landsliding at which variations in soil and vegetation become important. On natural slopes positive pore pressures occur often at the weathering depth of the soil profile. At this critical depth root reinforcement is crucial to avert slope instability. This is particularly relevant for the abandoned slopes in the European part of the Mediterranean basin where root development has to balance the increasing infiltration capacity during re-vegetation. Detailed investigations related to root reinforcement were made at two abandoned slopes susceptible to landsliding located in the Alcoy basin (SE Spain). On these slopes semi-natural vegetation, consisting of a patchy herbaceous cover and dispersed Aleppo pine trees, has established itself. Soil and vegetation conditions were mapped in detail and large-scale, in-situ direct shear tests on the topsoil and pull-out tests performed in order to quantify root reinforcement under different vegetation conditions. These tests showed that root reinforcement was present but limited. Under herbaceous cover, the typical reinforcement was in the order of 0.6 kPa while values up to 18 kPa were observed under dense pine cover. The tests indicate that fine root content and vegetation conditions are important factors that explain the root reinforcement of the topsoil. These findings were confirmed by the simulation of the direct shear tests by means of an advanced root reinforcement model developed in FLAC 2D. Inclusion of the root distribution for the observed vegetation cover mimics root failure realistically but returns over-optimistic estimates of the root reinforcement. When the root reinforcement is applied with this information at the hillslope scale under fully saturated and critical hydrological conditions, root pull-out becomes the dominant root failure mechanism and the slip plane is located at the weathering depth of the soil profile where root reinforcement is negligible. The safety factors increase only slightly when roots are present but the changes in the surface velocity at failure are more substantial. Root reinforcement on these natural slopes therefore appears to be limited to a small range of critical hydrological conditions and its mitigating effect occurs mainly after failure.


FLAC 2D in-situ direct shear tests root pull-outs root reinforcement slope stability modelling vegetation 


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  1. Abe, K, Ziemer, R R 1991Effect of tree roots on shallow-seated landslides USDA Forest ServiceGen. Tech. Rep.1301120PSW-GTR-Google Scholar
  2. Allison, L H 1935Organic soil carbon reduction of chromic acidSoil Sci.40311320Google Scholar
  3. BS 1990 Methods of test for soils for civil engineering purposes. Shear strength tests (effective stress). BS 1377-8, British Standards Institute.Google Scholar
  4. Cammeraat L H, Van Beek L P H and Kooijman A Vegetation succession and its consequences for slope stability in SE Spain. Plant Soil 278, 135–147.Google Scholar
  5. Cammeraat L H, Van Beek L P H and Dorren L K 2002 Eco-Slopes Field Protocol. University of Amsterdam. 73 pp.Google Scholar
  6. Danjon, F, Bert, D, Godin, C, Trichet, P 1999Structural root architecture of 5-year-old Pinus pinaster measured by 3D digitising and analysed with AMAPmodPlant Soil2174963CrossRefGoogle Scholar
  7. Dawson, E M, Roth, W H, Drescher, A 1999Slope stability analysis by strength reductionGéotechnique49835840Google Scholar
  8. Drexhage, M, Gruber, F 1999Above- and below-stump relationships for Picea Abies: Estimating root system biomass from breast-height diametersScand. J. Forest. Res.14328333Google Scholar
  9. FAO1990Guidelines for Soil Profile Description, 2nd edition. Soil Survey and Fertility Branch Land and Water Development Division.FAORomeGoogle Scholar
  10. Fourcaud T, Danjon F and Dupuy L, 2003. Numerical analysis of the anchorage of maritime pine trees in connection with root structure In Wind Effects on Trees. (Eds.) B Ruck et al. Int. Conf., Karlsruhe. pp. 323–329.Google Scholar
  11. Genet M 2004 Le rôle de la cellulose dans le résistance a la traction des racines DEA Sciences du Bois LRBB. 28 pp.Google Scholar
  12. GEO 2000 Geotechnical Manual for Slopes. 4th reprint. Geotechnical Engineering Office. The Government of the Hong Kong Special Administrative Region, Hong Kong.Google Scholar
  13. Gray, D H 1995Influence of vegetation on the stability of slopesBarker, D H eds. Vegetation and SlopesInstitution of Civil EngineersLondon225Google Scholar
  14. Itasca 2002 FLAC 4.0 User Manual.Google Scholar
  15. La Roca-Cervigón N and Calvo-Cases A 1988 Slope evolution by mass movements and surface wash (Valls d’Alcoi, Alicante, Spain). In Eds. A Imeson and M Sala. Geomorphic Processes Vol. I: pp 95–102 Hillslope Processes. Catena Verlag, Cremlingen.Google Scholar
  16. La Roca-Cervigón, N 1991Untersuchungen zur räumlichen und zeitlichen Variabilität der Massenbewegungen in Einzuchsgebiet des Riu d’Alcoi (Alicante, Ostspanien)Erde122221236Google Scholar
  17. Lamas, F, Irigaray, C, Chacón, J 2002Geotechnical characterisation of carbonate marlsfor the construction of impermeable dam coresEng. Geol.66283294CrossRefGoogle Scholar
  18. LI-COR 1990 LAI-2000 Plant Canopy Analyzer. Instruction Manual. LI-COR, Lincoln, NE.Google Scholar
  19. MacDonald, D, Crabtree, J R, Wiesinger, G, Dax, T, Stamou, N, Fleury, P, Gutierrez-Lazpita, J, Gibon, A 2000Agricultural abandonment in mountain areas of Europe: Environmental consequences and policy responseJ. Environ. Manage.594769CrossRefGoogle Scholar
  20. Mulder H F M 1991 Assesment of landslide hazard. Doct. Thesis. Utrecht University, 150 pp.Google Scholar
  21. O’Loughlin, C L 1974The effect of timber removal on the stability of forest soilsNew Zeal. J. Hydrol.12121134Google Scholar
  22. Riestenberg M M 1994. Anchoring of Thin Colluvium by Roots of Sugar Maple and White Ash on Hillslopes in Cincinnati. U.S Geological Survey, Bulletin 2059-E. United States Government Printing Office, Washington DC, 25 pp.Google Scholar
  23. Schmidt, K M, Roering, J J, Stock, J D, Dietrich, W E, Montgomery, D R, Schaub, T 2001The variability of root cohesion as an influence on shallow landslide susceptibility in the Oregon Coast RangeCan. Geotech. J.389951024CrossRefGoogle Scholar
  24. Sidle R C, Pearce A J and O’Loughlin C O 1985 Hillslope Stability and Land Use. AGU Water Resources Monograph 11.Google Scholar
  25. Skempton, A W 1985Residual strength of clays in landslides, folded strata and the laboratoryGéotechnique35318Google Scholar
  26. Tsakumoto Y and Kusakabe O 1984 Vegetative influences on debris slide occurrences on steep slopes in Japan. In Proc. Symp. Effects Forest Land Use on Erosion and Slope Stability. Environment and Policy Institute, Honolulu.Google Scholar
  27. USACE, 1983. Engineering Properties of Soil and Rock. United States Army Corps of Engineers, TM 5-818-1/AFM 88-3 Ch. 7, Chapter 3, Washington, 27 pp.Google Scholar
  28. Van Beek L P H 2002 Assessment of the Influence of Changes in Land Use and Climate on Landslide Activity in a Mediterranean Environment. Netherlands Geographical Studies 294, KNAG, Utrecht, 364 pp.Google Scholar
  29. Vidal H, 1966. La terre armée. Annales Institut Technique Batim., Paris, No. 223–229: 888–939.Google Scholar
  30. Waldron, L J 1977The shear resistance of root-permeated homogeneous and stratified soilSoil Sci. Soc. Am. J.41843848CrossRefGoogle Scholar
  31. Wu, T H 1984Effect of Vegetation on Slope Stability. Transportation Research Record 965Transportation Research BoardWashington, DC3746Google Scholar
  32. Wu, T H, McKinnel, W P, Swanston, D N 1979Strength of tree roots and landslides on Prince of Wales Island, AlaskaCan. Geotech. J.161933CrossRefGoogle Scholar
  33. Wu, T H, Beal, P E, Chinchun, L 1988In-situ shear test of soil–root systemsJ. Geotech. Eng.-ASCE11413771393Google Scholar
  34. Wu, T H 1995Slope stabilizationMorgan, R P CRickson, R J eds. Slope Stabilization and Erosion ControlSponLondon221264Google Scholar
  35. Wesemael, J C 1955De bepaling van het calciumcarbonaatgehalte van grondenChemisch Weekblad513536Google Scholar
  36. Yarbrough L D 2000 Channel bank stability and design-considering the effects of riparian vegetation and root reinforcement. M.Sc. Thesis, University of Mississippi, 139 pp.Google Scholar

Copyright information

© Springer 2005

Authors and Affiliations

  • L. P. H. van Beek
    • 1
  • J. Wint
    • 2
  • L. H. Cammeraat
    • 3
  • J. P. Edwards
    • 4
  1. 1.Department Of Physical Geography, Utrecht Centre of GeosciencesUtrecht UniversityUtrechtThe Netherlands
  2. 2.Department of Civil EngineeringNottingham trent UniversityUK
  3. 3.IBED-Physical GeographyUniversity of AmsterdamThe Netherlands
  4. 4.Scott Wilson Pavement Engineering Ltd.NottinghamUK

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